Drill.



L. W. PRATT.

DRILL.

APPLIOATION FILED JULY 2a, 1909.

985,283, Patented Feb.28, 1911.

Zflitnesses. Inventor.

ass at LLOYD W. PRATT, OF TAUNTON, MASSACHUSETTS, ASSIGNOR TO NEWPROCESS TWIST DRILL COMPANY, OF TAUNTON, MASSACHUSETTS, A CORPORATION OFMASSA- CHUSETTS.

DRILL.

Specification of Letters Patent.

Patented Feb. 28, 1911.

b all whom it may concern:

Be it known that I, LLoYn XV. PRATT, of Taunton, in the county ofBristol and State of Massachusetts, have invented certain new and usefulImprovements in Drills, of which the following is a specification,reference being had to the accompanying drawings, forming part thereof.

This invention has reference to improvements in drills and particularlyto drills having blades having parallel sides.

The object of the invention is to so provide a drill blade formed offlat material with a cylindrical shank without unduly weakening theshank or the point of juncture between the blade and the shank andwithout materially increasing the cost of the same,

The invention consists in the drill as hereinafter described andclaimed.

Figure 1, represents an elevation of the improved drill, parts of theblade being broken away. Fig. 2, represents a sectional view of the sametaken on line 22 Fig. 1. Fig. 3, represents a sectional view of parts ofthe same taken on line 33 Fig. 2, the portion of the blade being shownin full. Fig. 4, represents an end view of the shank to indicate themanner in which the socket is formed therein. Fig. 5, represents asectional view taken on line 55 Fig. 3, looking in the directionindicated by the arrows.

Similar numbers of reference designate corresponding parts throughout.

Drill blades of the nature particularly referred to herein are generallyconstructed from expensive high grade steel and are adapted for highspeed machine work. As a matter of economy, as well as to facilitate theprocess of manufacture, the blades are generally formed fromapproximately flat stock or stock having fiat sides, the stock beingtwisted and the edges then finished and ground. In order to adapt theseblades to the holding devices of well known construction in general useit is desirable that the blades should be furnished with cylindrical,preferably tapering, shanks. Owing to the high cost of tungsten or otherspecial steel from which the blade is formed and to the exigencies ofits use it is desirable that the drill shanks should be formed of adifferent grade or quality of steel and that the blade should be rigidlyfixed to the shank.

In carrying this invention into practice I take a shank 5 of any usualshape and size preferably having a conical taper and the cylindricalenlargement 6. In the end 7 of said enlargement I drill two holes 8-S;at distances from the periphery of the enlargement, and the materialbetween these holes I cut away, preferably by milling, thereby forming asocket extending parallel with the shank and having flat sides andcurved ends. I now take the blade 9, usually having approximatelyrectangular edges, and, at the shank end thereof, I grind or shape suchedges to form a tang, beyond the squared shoulders 1010, which tang hasthe flat sides 1l-11 and the rounded edges 12-l2 adapted to closely fitthe corresponding parts of the socket above described. The tang oftheblade 9 is now inserted in the socket of the shank 5 and said bladeis driven home until its shoulders 101O bear against the end 7 of theshank after which these parts are brazed together. By this constructionthe tang of the blade 9 is embraced by a solid Wall of the material ofthe shank and is held firmly in place by a single continuous body ofmaterial. In use torsional strain on the blade 9 is resisted not only bythe tensile strength of the peripheral portions of the shank but by thesolid bodies of material bearing against the sides of the blade tang.

Having thus described my invention, I claim as new and desire to secureby Letters Patent A drill comprising a blade rectangular in crosssection and terminating in a tang having rounded edges, located withinthe cross sectional area of said blade, and fiat sides in the surfaceplanes of the sides of said blade, whereby shoulders are formed on theend of said blade, and a shank having a socket having fiat walls andcurved end walls to receive and closely embrace said tang, saidshoulders of the blade bearing against the end of said shank at pointsseparated from each other.

LLOYD TV. PRATT. lVi tnesses H. J. MILLER, M. M. HAnmNo'roN.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents,

